AFM working principles and modes: (a) generalized schematic of AFM of cantilever with the laser reflecting onto the photodetector. (b) Tapping/dynamic mode. (c) Contact mode. (d) Friction/lateral mode. (e) Phase imaging from dynamic mode, where the contrast (butadiene/styrene blend) relates to surface properties. (f) Kelvin probe electrical imaging; contrast shows surface potential (work function) of a graphene flake on SiO2 substrate. (g) Magnetic mode imaging, where a magnetic coated cantilever scans just above the surface and the phase shift relates to attraction/repulsion of magnetic domains (images courtesy of Hitachi High Technology, Tokyo, Japan).